A 20-year-old Oakton High graduate who played football and rowed crew at the Fairfax County school was arrested Wednesday as an alleged terrorist recruit after he had been stopped on his way to join an al-Qaeda-linked group in Somalia, federal officials said.

Zachary Adam Chesser was barred July 10 from leaving New York City for Uganda on a multi-leg journey to join al-Shabab, an Islamist insurgency that wants to topple Somalia's weak central government, according to the FBI and papers filed Wednesday in U.S. District Court in Alexandria.

Chesser made his first court appearance before U.S. Magistrate Judge Theresa C. Buchanan in Alexandria Thursday morning. Unshaven and dressed in a short-sleeved blue shirt, cargo pants, white socks and athletic shoes, the brown-haired Chesser's only words came after Buchanan asked if he wanted a lawyer, saying, "Um, please appoint one." The judge ordered Chesser held until another hearing at 2:30 p.m. Friday.

In diary entries, personal e-mails and interviews with federal agents detailed in court papers, Chesser described in haunting terms a two-year descent from a quiet and awkward suburban teenager to a willing "foreign fighter" for a designated terrorist group, which most recently claimed responsibility for bombings that killed 76 people in Uganda on July 11.

Chesser, who was identified with a terrorist group for the first time, is charged with trying to join al-Shabab. There's no indication that he carried out any act of terrorism. But counterterrorism analysts warn that his evolution from propagandist to alleged terrorist-enlistee exemplifies the growing trend of young Americans whose passports and appearance make them valued potential operatives.

Another recent example includes five young men from the Alexandria area who were convicted in Pakistan of trying to join the fight against the United States in Afghanistan. Many of the suspects contacted al-Qaeda or related groups in Pakistan, Afghanistan, Yemen and other countries via the Internet, and slipped away from their families.

"The significance of this case is the proliferation of U.S. citizens who are becoming radicalized -- eating and drinking up propaganda and taking steps on behalf of terrorist causes," said a federal law enforcement official who spoke on condition that he not be named because he is not authorized to speak to the media.

Megan Chesser, his stepmother, said the family would not comment. Relatives of his wife also declined to comment.

Supporters of Chesser at the courthouse Thursday morning, who declined to say if they were his relatives, included a young woman dressed in a black burqa and veil with only her eyes showing, and two other women and a man. All declined comment.

Chesser, a George Mason University dropout whose parents live in Centreville, told the FBI that he only recently became religious and grew a beard, took the name Abu Tallah Al-Amrikee and married a Muslim woman in 2009, according to court papers. He allegedly looked to online videos, chats and over-the-counter CDs "almost obsessively," before creating a stream of YouTube sites, blogs and postings spreading the call "to fight jihad," the papers say.

In particular, he said he exchanged e-mails directly with the Yemeni cleric Anwar al-Aulaqi, who helped direct Umar Farouk Abdulmutallab's attempt to blow up a Detroit-bound plane on Christmas. U.S. authorities have designated the U.S.-born Aulaqi as a global terrorist and targeted him for killing.

In a July 13, 2009, e-mail sent from his GMU account and obtained by court order, Chesser asked Aulaqi "for an interpretation" of two dreams he had, explaining that he "had prayed to Allah to let him be in Al-Shabaab."

In an October 2009 diary entry obtained through a search warrant at his home, Chesser wrote, "I ask Allah to make [my writings] a source of inspiration as well as a real-life 'how-to-guide' on how to reach the fields of Jihad."

He said he stopped talking with his mother, who received death threats for his "South Park" posting, while his mother-in-law hid his wife's passport to prevent her from going overseas with him.

"These allegations underscore the need for continued vigilance against homegrown terror threats," U.S. Attorney Neil H. MacBride said in a statement.

"We can't fight terrorists alone," said Shawn Henry, assistant director in charge of the FBI's Washington Field Office. "Religious leaders of all faiths, family members and particularly the younger members of our communities need to speak up and speak out against individuals who participate in actions like those alleged here."

In April, Chesser wrote about "South Park's" creators on the Revolution Muslim blog, posting, "We have to warn Matt [Stone] and Trey [Parker] that what they are doing is stupid and they will probably wind up like Theo Van Gogh," a Dutch filmmaker killed in 2004 after he attacked the treatment of women in Islamic society.

"This is not a threat, but a warning of the reality of what will likely happen to them," he wrote.

Court filings do not say what first drew Chesser to the FBI's attention. But he was interviewed by Special Agent Paula G. Menges in May and June 2009. Chesser told her that he had created YouTube sites such as AlQuranWaAlaHadeeth and Themujahidblog.com, and posted numerous videos and chats advocating his desire to "LearnTeachFightDie" for Islam, as one of his usernames stated, according to court papers.

Chesser had tried to travel to Somalia via Kenya in November 2009 to join al-Shabab but decided against it because his mother-in-law hid the passport belonging to his wife, Proscovia Nzabanita, the court papers say.

After being told he was on the no-fly list July 10, Chesser was released. It is not clear where he went, but he contacted Menges again July 14, saying he had planned to join al-Shabab but had a "change of heart" after the Ugandan bombings, the court papers say.

Chesser said he planned to travel to Uganda by way of Dubai and Ethiopia, and from there, go to Kenya and bribe a border guard for as little as $20 to enter Somalia, court papers say. In court-ordered wiretaps, he told his wife that he would be in Uganda for a day and would fly with their infant son as part of his "cover."

He told the FBI that al-Shabab wanted laptops and cameras and planned six-week boot camps starting after Ramadan, the Muslim holiday, this fall.

Ibrahim Al-Khalaf, a 2009 graduate of Oakton High School and a former president of the Muslim Students Association, said he thought Chesser converted to Islam his senior year. "He was a really nice kid. He smiled at everybody," Al-Khalaf said.

But Chesser criticized other students' faith at MSA meetings. "We were more liberal, and we used to try to educate everybody and create a positive environment," Al-Khalaf said. "But Zach would say, 'If you do this, you are going to hell. If you do that, you are going to hell.' "